<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <link href="https://cdn.bootcdn.net/ajax/libs/minireset.css/0.0.2/minireset.min.css" rel="stylesheet" />
  </head>
  <body>
    <style>
      main {
        width: 300px;
        height: 300px;
        display: grid;
        grid-template-rows: repeat(3, 1fr);
        grid-template-columns: repeat(3, 1fr);
      }
      main div {
        background-color: slateblue;
        background-clip: content-box;
        padding: 5px;
        border: solid 1px #ddd;
      }
      main div:first-child {
        grid-row-start: 1;
        grid-row-end: 2;
        grid-column-start: 1;
        grid-column-end: 4;
      }
      main div:nth-child(2) {
        grid-row-start: 2;
        grid-row-end: 4;
        grid-column-start: 1;
        grid-column-end: 2;
      }
      main div:nth-child(3) {
        grid-row-start: 2;
        grid-row-end: 4;
        grid-column-start: 2;
        grid-column-end: 4;
      }
    </style>
    <main>
      <div></div>
      <div></div>
      <div></div>
    </main>
  </body>
</html>
